bughunter writes "The Orbiting Carbon Observatory (OCO) is slated for launch tomorrow, February 24, 2009. OCO is the first earth science observatory that will create a detailed map of atmospheric carbon dioxide sources and sinks around the globe. And not a moment too soon. Popular Mechanics has a concise article on the science that this mission will perform, and how it fits in with the existing 'A-train' of polar-orbiting earth observatories. JPL's page goes into more detail. And NASA's OCO Launch Blog will have continuous updates as liftoff approaches and the spacecraft reports in and checks out from 700km up."